Electronic devices often include a switched-mode power supply (SMPS) DC-to-DC converter, which can also be referred to herein simply as a DC-DC converter, to adjust (step-up or step-down) and stabilize voltage levels. For example, portable electronic devices, such as mobile phones, laptop computers and tablets often use such a DC-to-DC converter to adjust an input voltage level supplied by a battery to the appropriate level for powering circuitry within such devices. A boost DC-to-DC converter steps up an input voltage to a higher output voltage. A buck DC-to-DC converter steps down the input voltage so that the output voltage is lower than the input voltage.
In SMPS DC-to-DC converters, power loss results from either current conduction loss or switching loss in a power switch. Under heavy load conditions, current is high and thus conduction loss is the dominant factor. However, under light load conditions, current is low and thus switching loss is the dominant factor. To improve the light load efficiencies of a DC-to-DC converter, multiple modulation modes can be used to control the DC-to-DC converter at different output current (i.e., load) conditions. For example, in order to optimize the power efficiency for all load conditions, a SMPS DC-to-DC converter typically uses pulse width modulation (PWM) in heavy load conditions and pulse frequency modulation (PFM) in light load conditions.